The present invention generally relates to automotive sensors, and more particularly to a system for the combined detection of hub temperature and wheel speed.
Wheel speed sensors are used in motor vehicles in a number of applications, including control of anti-lock brake system or traction-control systems. Such wheel speed sensors preferably make a non-contact observation of the rotation of the wheel, both to avoid interference with the wheel""s movement and to avoid the difficulty of transmitting a signal from the rotating wheel to the vehicle. Wheel speed sensors making such a non-contact observation typically couple to the wheel a rotor having a magnetic element. The magnetic element typically creates a magnetic field with alternating magnetic flux lines at some radial position relative to the wheel""s axis of rotation. A circuit containing a magnetic field sensor, such as a Hall effect sensor, is typically located at that position but separately from the rotor assembly, and not coupled to the wheel. The magnetic field sensor detects the alternating magnetic flux as the wheel rotates and causes the circuit to produce a signal responsive to the rate of alternation in the flux lines, and therefore proportional to the angular speed of the wheel.
For certain applications, additional formation is useful for monitoring the performance of the wheels of a vehicle. One piece of additional information that may be valuable is the direction of the wheel""s rotation. It may therefore be preferable in some applications to generate a signal indicating the wheel""s angular velocity (that is, both its angular speed and direction of rotation), rather than just its angular speed. Another piece of information that may be especially valuable is the temperature of the bearings upon which the wheel is rotating. In particular, in the case of towed vehicles, it is desirable to observe the temperature of the bearings as a means for early detection of a mechanical failure or impending mechanical failure.
Sensing all of these (or a plurality of these) parameters on a single wheel can become cumbersome due to the number of sensors required. There is therefore a need for a sensor that can measure multiple parameters of a rotating wheel. The present invention is directed toward meeting this need.
A system for detecting the angular velocity and temperature of a rotating member according to the present invention include a temperature sensor in proximity to a rotational mounting of the rotating member. The temperature sensor is adapted to produce a temperature signal corresponding to a temperature of a portion of the rotating member. The system further comprises a rotation-indicating element affixed to the rotating member, at least one rotation-detecting element adapted to detect rotational motion of said rotation-indicating element and a processing element in communication with said temperature sensor and said rotation-detecting element. The processing element is adapted to produce a signal corresponding to an angular velocity of the rotating member and a temperature observed by said temperature sensor.
One exemplary system according to the present invention comprises a temperature sensor adapted to produce a temperature signal and in proximity to a wheel bearing upon which the wheel is mounted. The system also comprises a magnet affixed to the wheel and adapted to produce a magnetic flux through a fixed area that regularly oscillates as the wheel rotates. The system further comprises at least two Hall effect sensors positioned to detect magnetic flux through said fixed area in quadrature. The system further comprises a processing element in communication with the temperature sensor and the at least two Hall effect sensors. The processing element is adapted to produce a signal corresponding to an angular velocity of the wheel and a temperature observed by said temperature sensor. The processing element comprises a logic element responsive to said at least two Hall effect sensors to produce a speed signal corresponding to an angular speed of said wheel and a direction signal corresponding to a direction of rotation of said wheel. The processing element also comprises a first sub-circuit, a second sub-circuit, and a switch responsive to the direction signal to cause said temperature signal to be sent on the first sub-circuit when the wheel has a first direction of rotation, and to cause the temperature signal to be sent on the second sub-circuit when the wheel has a second direction of rotation.
Other objects and advantages of a system according to the present invention will be apparent to those skilled in the art.